The present invention relates to a gas laser generator having improved gas cooling ducts.
It is generally desired that the laser beam produced by a gas laser generator has the Gaussian distribution profile of energy flux. Namely, when the energy density of the laser beam is plotted on the vertical axis against the distance of a point from the center of the laser beam on the horizontal axis, the Gaussian distribution is characterized by an extremely high energy density at the central portion of the laser beam relative to that at points in the peripheral region ranging from an intermediate point which slightly comes off the beam center to a point on the outer boundary of the beam. The higher the energy density at the central portion than that in the peripheral region, better is the converging characteristics of the laser beam. In cutting or welding steel plates using a laser beam, the better laser converging characteristics allow a narrower cut or welded portion, resulting in a precise machining and reduction of machining time.
The gas laser generator can produce a laser beam with the better converging characteristics by using a long discharge tube with a small diameter. A long discharge tube is made by joining a plurality of discharge tubes each having a discharge section, and it is formed in a crank structure to avoid longitudinal dimension which is too large. For example, a gas laser generator disclosed in U.S. Pat. No. 4,351,052 has the structure of two discharge tubes disposed in parallel with discharge sections located at the right and left portions of each tube. A common vessel connects the ends of both discharge tubes to form a complete discharge tube structure. The end sections and intermediate sections of the discharge tube structure are provided with two systems of cooling ducts, each system including a heat exchanger and a centrifugal blower. By the operation of the centrifugal blowers, a mixture gas, e.g., CO.sub.2, He and N.sub.2, circulates through the discharge tubes and cooling ducts, and the interior of the discharge tube structure is cooled. This arrangement, however, uses two centrifugal blowers in two systems, making the arrangement of the cooling ducts complex. This makes the smooth feeding of the mixture gas into the discharge tubes difficult, resulting in a lower laser output. The operation of two centrifugal blowers increases the vibration, resulting possibly in a positional error of the reflectors and output mirror.